# ERC-721 Safe Transfer Calldata Builder

> ERC-721 Safe Transfer Calldata Builder is a paid API for AI agents from evm-canon-base.onrender.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Encodes ERC-721 safeTransferFrom calldata for NFT transfers on EVM-compatible chains

## Facts

- Endpoint: POST https://evm-canon-base.onrender.com/encode/nft-transfer
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/erc-721-safe-transfer-calldata-builder-59cfeed7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_9wG9d6ZFdtVuWi24eoASN

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability erc-721-safe-transfer-calldata-builder-59cfeed7 -d '<json body>'
```

Example prompt: Build me the ERC-721 safeTransferFrom calldata to send token ID 42 from 0xAbCd...1234 to 0xDeFa...5678 on the NFT contract at 0x1234...abcd.

## When to prefer this

Choose this endpoint when you need to programmatically generate ERC-721 safeTransferFrom calldata without running a local Ethereum library. Ideal for agents or serverless workflows that need raw transaction data for NFT transfers without a full Web3 stack. Prefer this over manual ABI encoding when working with Base or other EVM chains in lightweight environments.

## Known failure modes

- Invalid or non-checksummed Ethereum address returns a 400 error
- Missing required fields (contract, from, to, tokenId) cause validation errors
- Malformed token ID (non-integer or negative) causes a 400 error
- Service unavailable on Render cold start may cause initial latency or timeout

## How this service works

Build ERC-721 safe transfer calldata

## Output

Returns hex-encoded ABI calldata for an ERC-721 safeTransferFrom function call, ready to be submitted as the data field of an EVM transaction. Includes the 4-byte function selector and encoded parameters for from address, to address, and token ID.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "args"
     ],
     "properties": {
      "args": {
       "type": "object",
       "description": "arguments keyed by parameter name"
      },
      "chain": {
       "description": "chain name, alias or numeric chainId"
      },
      "token": {
       "type": "string",
       "description": "symbol or contract address"
      },
      "value": {
       "type": "string",
       "description": "native value in wei"
      },
      "function": {
       "type": "string",
       "description": "name or full signature (generic route only)"
      }
     }
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/erc-721-safe-transfer-calldata-builder-59cfeed7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from evm-canon-base.onrender.com](https://www.zero.xyz/host/evm-canon-base.onrender.com/llms.txt)